System and method for defect detection and photoluminescence measurement of a sample

ABSTRACT

Defect detection and photoluminescence measurement of a sample directing a beam of oblique-illumination wavelength light onto a portion of the sample, directing a beam of normal-illumination wavelength light for causing one or more photoluminescing defects of the sample to emit photoluminescent light onto a portion of the sample, collecting defect scattered radiation or photoluminescence radiation from the sample, separating the radiation from the sample into a first portion of radiation in the visible spectrum, a second portion of radiation including the normal-illumination wavelength light, and at least a third portion of radiation including the oblique-illumination wavelength light, measuring one or more characteristics of the first portion, the second portion or the third portion of radiation; detecting one or more photoluminescence defects or one or more scattering defects based on the measured one or more characteristics of the first portion, the second portion or the third portion of radiation.

CROSS-REFERENCE TO RELATED APPLICATION

The present patent application constitutes a continuation application ofU.S. Non-Provisional patent application entitled SYSTEM AND METHOD FORDEFECT DETECTION AND PHOTOLUMINESCENCE MEASUREMENT OF A SAMPLE, namingROMAIN SAPPEY as inventor, filed Mar. 14, 2014, application Ser. No.14/212,496, which constitutes non-provisional patent application of U.S.Provisional patent application entitled PHOTOLUMINESCENCE AND DEFECTINSPECTION SYSTEMS AND METHODS, naming ROMAIN SAPPEY as inventor, filedJun. 26, 2013, Application Ser. No. 61/839,494. Both of the aboveapplications are incorporated herein by reference in the entirety.

TECHNICAL FIELD

The present invention generally relates to the detection andclassification of defects, in particular, the present invention relatesto the detection and classification of photoluminescence and scatteringdefects.

BACKGROUND

As demand for ever-shrinking semiconductor devices continues toincrease, so too will the demand for improved inspection tools fordefect identification and classification. Defects impacting the qualityof fabricated devices may include, for example, stacking fault defectsand basal plane dislocation defects. Stacking fault defects and basalplane dislocations display a weak photoluminescent signature whenstimulated with ultraviolet light. Current inspection tools do notefficiently measure photoluminescent defects in conjunction withscattering-type defects. As such, it is desirable to provide improvedmethods and systems that act to cure the defects of the prior art.

SUMMARY OF THE INVENTION

A system for defect detection and photoluminescence measurement of asample is disclosed. In one aspect, the system may include, but is notlimited to, an oblique-incidence radiation source configured to direct abeam of light of an oblique-illumination wavelength onto a portion ofthe sample along a direction oblique to the surface of the sample; anormal-incidence radiation source configured to direct a beam of lightof a normal-illumination wavelength different from theoblique-illumination wavelength onto a portion of the sample along adirection substantially normal to the surface of the sample, wherein thebeam of light of the normal-illumination wavelength is suitable forcausing one or more photoluminescing defects of the sample to emitphotoluminescent light; a sample stage assembly configured to secure thesample and selectively actuate the sample in order to perform a scanningprocess with at least the oblique-incidence radiation source and thenormal-incidence radiation source; a set of collection optics configuredto collect radiation from the sample, the radiation from the sampleincluding at least one of radiation elastically scattered by one or moredefects of the sample or photoluminescence radiation emitted by the oneor more photoluminescing defects of the sample; a filter sub-systemconfigured to receive at least a portion of the radiation collected bythe set of collection optics, wherein the filter sub-system isconfigured to separate the radiation from the sample into a firstportion of radiation including one or more wavelengths in the visible ornear-infrared spectrum associated with the light emitted by the one ormore photoluminescing defects of the sample, a second portion ofradiation including the normal-illumination wavelength, and at least athird portion of radiation including the oblique-illuminationwavelength; a detection sub-system including a first sensor formeasuring one or more characteristics of the first portion of radiationtransmitted by the filter sub-system, a second sensor for measuring oneor more characteristics of the second portion of radiation transmittedby the filter sub-system and at least a third sensor for measuring oneor more characteristics of the third portion of radiation transmitted bythe filter sub-system; and a controller communicatively coupled to thefirst sensor, the second sensor and the third sensor, the controllerconfigured to: detect one or more scattering defects based on at leastone of the one or more characteristics measured by the second sensor andthe third sensor; and detect one or more photoluminescence defects basedon at least one of the one or more characteristics measured by the firstsensor, the one or more characteristics measured by the second sensorand the one or more characteristics measured by the third sensor.

In another aspect, the system include, but is not limited to, anoblique-incidence radiation source configured to direct a beam of lightof an oblique-illumination wavelength onto a portion of the sample alonga direction oblique to the surface of the sample; a normal-incidenceradiation source configured to direct a beam of light of anormal-illumination wavelength different from the oblique-illuminationwavelength onto a portion of the sample along a direction substantiallynormal to the surface of the sample, wherein the beam of light of thenormal-illumination wavelength is suitable for causing one or morephotoluminescing defects of the sample to emit photoluminescent light; asample stage assembly configured to secure the sample and selectivelyactuate the sample in order to perform a scanning process with at leastthe oblique-incidence radiation source and the normal-incidenceradiation source; a set of collection optics configured to collectradiation from the sample, the radiation from the sample including atleast one of radiation elastically scattered by one or more defects ofthe sample or photoluminescence radiation emitted by the one or morephotoluminescing defects of the sample; a filter sub-system configuredto receive at least a portion of the radiation collected by the set ofcollection optics, wherein the filter sub-system is configured toseparate the radiation from the sample into a first portion of radiationincluding one or more wavelengths in the visible or near-infraredspectrum associated with the light emitted by the one or morephotoluminescing defects of the sample, a second portion of radiationincluding the normal-illumination wavelength, a third portion ofradiation including the oblique-illumination wavelength, and at least afourth portion of radiation including one or more wavelengths in theultraviolet spectrum associated with the photoluminescent light emittedby the one or more photoluminescing defects of the sample; a detectionsub-system including a first sensor for measuring one or morecharacteristics of the first portion of radiation transmitted by thefilter sub-system, a second sensor for measuring one or morecharacteristics of the second portion of radiation transmitted by thefilter sub-system, a third sensor for measuring one or morecharacteristics of the third portion of radiation transmitted by thefilter sub-system, and at least a fourth sensor for measuring one ormore characteristics of the fourth portion of radiation transmitted bythe filter sub-system; and a controller communicatively coupled to thefirst sensor, the second sensor and the third sensor, the controllerconfigured to: detect one or more scattering defects based on the lightmeasured by at least one of the second sensor and the third sensor; anddetect one or more photoluminescence defects based on the light detectedby at least one of the first sensor, the second sensor, the thirdsensor, and the fourth sensor by comparing a signal from at least one ofthe first sensor, the second sensor, the third sensor, and the fourthsensor in an area of the sample absent of photoluminescing defects to asignal from at least one of the first sensor, the second sensor, thethird sensor, and the fourth sensor acquired from a measured region ofthe sample.

In another aspect, the system may include, but is not limited to, anormal-incidence radiation source configured to direct a beam of lightof a normal-illumination wavelength onto a portion of the sample along adirection substantially normal to the surface of the sample, wherein thebeam of light of the normal-illumination wavelength is suitable forcausing one or more photoluminescing defects of the sample to emitphotoluminescent light; a sample stage assembly configured to secure thesample and selectively actuate the sample in order to perform a scanningprocess with at least the oblique-incidence radiation source and thenormal-incidence radiation source; a set of collection optics configuredto collect radiation from the sample, the radiation from the sampleincluding at least one of radiation elastically scattered by one or moredefects of the sample or photoluminescence radiation emitted by the oneor more photoluminescing defects of the sample; a filter sub-systemconfigured to receive at least a portion of the radiation collected bythe set of collection optics, wherein the filter sub-system isconfigured to separate the radiation from the sample into a firstportion of radiation including one or more wavelengths in the visible ornear-infrared spectrum associated with the light emitted by the one ormore photoluminescing defects of the sample, a second portion ofradiation including the normal-illumination wavelength, and at least athird portion of radiation including one or more wavelengths in theultraviolet spectrum associated with the light emitted by the one ormore photoluminescing defects of the sample; a detection sub-systemincluding a first sensor for measuring one or more characteristics ofthe first portion of radiation transmitted by the filter sub-system, asecond sensor for measuring one or more characteristics of the secondportion of radiation transmitted by the filter sub-system, and at leasta third sensor for measuring one or more characteristics of the thirdportion of radiation transmitted by the filter sub-system; and acontroller communicatively coupled to the first sensor, the secondsensor, and the third sensor, the controller configured to: detect oneor more scattering defects based on the light measured by the secondsensor; and detect one or more photoluminescence defects based on thelight detected by at least one of the first sensor and the third sensorby comparing a signal from at least one of the first sensor and thethird sensor in an area of the sample absent of photoluminescing defectsto a signal from at least one of the first sensor and the third sensoracquired from a measured region of the sample.

In another aspect, the system may include, but is not limited to, anormal-incidence radiation source configured to direct a beam of lightof a normal-illumination wavelength onto a portion of the sample along adirection substantially normal to the surface of the sample, wherein thebeam of light of the normal-illumination wavelength is suitable forcausing one or more photoluminescing defects of the sample to emitphotoluminescent light; a sample stage assembly configured to secure thesample and selectively actuate the sample in order to perform a scanningprocess with at least the oblique-incidence radiation source and thenormal-incidence radiation source; a set of collection optics configuredto collect radiation from the sample, the radiation from the sampleincluding at least one of radiation elastically scattered by one or moredefects of the sample or photoluminescence radiation emitted by the oneor more photoluminescing defects of the sample; a filter sub-systemconfigured to receive at least a portion of the radiation collected bythe set of collection optics, wherein the filter sub-system isconfigured to separate the radiation from the sample into a plurality ofportions of photoluminescent radiation, each portion including one ormore wavelengths in a different spectral range of the radiation emittedby the one or more photoluminescing defects of the sample; a detectionsub-system including a plurality of sensors, each sensor suitable formeasuring one or more characteristics of one of the plurality ofportions of photoluminescent radiation transmitted by the filtersub-system; and a controller communicatively coupled to each of theplurality of sensors, the controller configured to: detect one or morephotoluminescence defects based on the light detected by each of theplurality of sensors by comparing a signal from at least one of theplurality of sensors in an area of the sample absent of photoluminescingdefects to a signal from at least one the plurality of sensors acquiredfrom a measured region of the sample; and classify the one or moredetected photoluminescence defects based on one or more signals measuredby each of the plurality of sensors.

A method for defect detection and photoluminescence measurement of asample is disclosed. In one embodiment, the method may include, but isnot limited to, directing a beam of oblique-illumination wavelengthlight onto a portion of the sample along a direction oblique to thesurface of the sample; directing a beam of normal-illuminationwavelength light onto a portion of the sample along a directionsubstantially normal to the surface of the sample, wherein the beam oflight of the normal-illumination wavelength is suitable for causing oneor more photoluminescing defects of the sample to emit photoluminescentlight; collecting radiation from the sample, the radiation from thesample including at least one of radiation elastically scattered by oneor more defects of the sample or photoluminescence radiation emitted bythe one or more photoluminescing defects of the sample; separating theradiation from the sample into a first portion of radiation includingone or more wavelengths in the visible spectrum associated with thelight emitted by the one or more photoluminescing defects of the sample,a second portion of radiation including the normal-illuminationwavelength light, and at least a third portion of radiation includingthe oblique-illumination wavelength light; measuring one or morecharacteristics of at least one of the first portion of radiation, thesecond portion of radiation and the third portion of radiation;detecting one or more scattering defects based on the measured one ormore characteristics of at least one of the second portion of radiationand the third portion of radiation; and detecting one or morephotoluminescence defects based on the measured one or morecharacteristics of at least one of the first portion of radiation, thesecond portion of radiation and the third portion of radiation bycomparing the one or more characteristics of at least one of the firstportion of radiation, the second portion of radiation and the thirdportion of radiation acquired from an area of the sample absent ofphotoluminescing defects to one or more characteristics of at least oneof the first portion of radiation, the second portion of radiation andthe third portion of radiation acquired from a measured region of thesample.

In another aspect, the method may include, but is not limited to,directing a beam of oblique-illumination wavelength light onto a portionof the sample along a direction oblique to the surface of the sample;directing a beam of normal-illumination wavelength light along adirection substantially normal to the surface of the sample, wherein thebeam of light of the normal-illumination wavelength is suitable forcausing one or more photoluminescing defects of the sample to emitphotoluminescent light; collecting radiation from the sample, theradiation from the sample including at least one of radiationelastically scattered by one or more defects of the sample orphotoluminescence radiation emitted by the one or more photoluminescingdefects of the sample; separating the radiation from the sample into afirst portion of radiation including one or more wavelengths in thevisible or near-infrared spectrum associated with the light emitted bythe one or more photoluminescing defects of the sample, a second portionof radiation including the normal-illumination wavelength, a thirdportion of radiation including the oblique-illumination wavelength andat least a fourth portion of radiation including one or more wavelengthsin the ultraviolet spectrum associated with the photoluminescent lightemitted by the one or more photoluminescing defects of the sample;measuring one or more characteristics of at least one of the firstportion of radiation, one or more characteristics of the second portionof radiation, one or more characteristics of the third portion ofradiation and one or more characteristics of the fourth portion ofradiation; detecting one or more scattering defects based on themeasured one or more characteristics of at least one of the secondportion of radiation and the third portion of radiation; and detectingone or more photoluminescence defects based on the measured one or morecharacteristics of at least one of the first portion of radiation, thesecond portion of radiation, the third portion of radiation and thefourth portion of radiation by comparing the one or more characteristicsof at least one of the first portion of radiation, the second portion ofradiation, the third portion of radiation and the fourth portion ofradiation acquired from an area of the sample absent of photoluminescingdefects to one or more characteristics of at least one of the firstportion of radiation, the second portion of radiation, the third portionof radiation and the fourth portion of radiation acquired from ameasured region of the sample.

In another aspect, the method may include, but is not limited to,directing a beam of normal-illumination wavelength light along adirection substantially normal to the surface of the sample, wherein thebeam of light of the normal-illumination wavelength is suitable forcausing one or more photoluminescing defects of the sample to emitphotoluminescent light; collecting radiation from the sample, theradiation from the sample including at least one of radiationelastically scattered by one or more defects of the sample orphotoluminescence radiation emitted by the one or more photoluminescingdefects of the sample; separating the radiation from the sample into afirst portion of radiation including one or more wavelengths in thevisible or near-infrared spectrum associated with the light emitted bythe one or more photoluminescing defects of the sample, a second portionof radiation including the normal-illumination wavelength and at least athird portion of radiation including one or more wavelengths in theultraviolet spectrum associated with the photoluminescent light emittedby the one or more photoluminescing defects of the sample; measuring oneor more characteristics of at least one of the first portion ofradiation, one or more characteristics of the second portion ofradiation and one or more characteristics of the third portion ofradiation; detecting one or more scattering defects based on themeasured one or more characteristics of at least one of the secondportion of radiation and the third portion of radiation; and detectingone or more photoluminescence defects based on the measured one or morecharacteristics of at least one of the first portion of radiation, thesecond portion of radiation, and the third portion of radiation bycomparing the one or more characteristics of at least one of the firstportion of radiation, the second portion of radiation and the thirdportion of radiation acquired from an area of the sample absent ofphotoluminescing defects to one or more characteristics of at least oneof the first portion of radiation, the second portion of radiation andthe third portion of radiation acquired from a measured region of thesample.

In another aspect, the method may include, but is not limited to,directing a beam of normal-illumination wavelength light onto a portionof the sample along a direction substantially normal to the surface ofthe sample, wherein the beam of light of the normal-illuminationwavelength is suitable for causing one or more photoluminescing defectsof the sample to emit photoluminescent light; collecting radiation fromthe sample, the radiation from the sample including at least one ofradiation elastically scattered by one or more defects of the sample orphotoluminescence radiation emitted by the one or more photoluminescingdefects of the sample; separating the radiation from the sample into aplurality of portions of photoluminescent radiation, each portionincluding one or more wavelengths in a different spectral range of thelight emitted by the one or more photoluminescing defects of the sample;measuring one or more characteristics of each of the plurality ofportions of photoluminescent radiation; detecting one or morephotoluminescence defects based on the measured one or morecharacteristics of each of the plurality of portions of photoluminescentradiation; and classifying the one or more detected photoluminescencedefects based on one or more signals associated with each of theplurality of portions of photoluminescent radiation.

In another aspect, the method may include, but is not limited to,directing a beam of normal-illumination wavelength light onto a portionof the sample along a direction substantially normal to the surface ofthe sample, wherein the beam of light of the normal-illuminationwavelength is suitable for causing one or more photoluminescing defectsof the sample to emit photoluminescent light; directing a beam ofoblique-illumination wavelength light onto a portion of the sample alonga direction along a direction oblique to the surface of the sample;collecting radiation from the sample, the radiation from the sampleincluding at least one of radiation elastically scattered by one or moredefects of the sample or photoluminescence radiation emitted by the oneor more photoluminescing defects of the sample; separating the radiationfrom the sample into a visible portion of photoluminescent radiation anda near ultraviolet (NUV) portion of photoluminescent radiation;measuring one or more characteristics of the visible portion ofphotoluminescent radiation and the NUV portion of photoluminescentradiation; detecting one or more photoluminescence defects based on themeasured one or more characteristics of the visible portion ofphotoluminescent radiation and the NUV portion of photoluminescentradiation; and classifying the one or more detected photoluminescencedefects based on one or more signals associated with the visible portionof photoluminescent radiation and the NUV portion of photoluminescentradiation.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not necessarily restrictive of the invention as claimed. Theaccompanying drawings, which are incorporated in and constitute a partof the specification, illustrate embodiments of the invention andtogether with the general description, serve to explain the principlesof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The numerous advantages of the disclosure may be better understood bythose skilled in the art by reference to the accompanying figures inwhich:

FIG. 1A illustrates a simplified schematic view of a system for defectdetection and photoluminescence measurement of a sample, in accordancewith one embodiment of the present invention.

FIG. 1B illustrates a set of spectral integration bins superposed on aphotoluminescent spectrum, in accordance with one embodiment of thepresent invention.

FIG. 1C illustrates a conceptual view of an inspection path of a spiralscan inspection system, in accordance with one embodiment of the presentinvention.

FIG. 1D illustrates a simplified schematic view of a system for defectdetection and photoluminescence measurement of a sample, in accordancewith one embodiment of the present invention.

FIG. 1E illustrates a set of spectral integration bins superposed on aphotoluminescent spectrum, in accordance with one embodiment of thepresent invention.

FIG. 1F illustrates a imagery data of a stacking fault defect and abasal plane dislocation acquired in dark contrast mode and brightcontrast mode, in accordance with an embodiment of the presentinvention.

FIG. 1G illustrates a simplified schematic view of a system for defectdetection and photoluminescence measurement of a sample, in accordancewith one embodiment of the present invention.

FIG. 1H illustrates a simplified schematic view of a system for defectdetection and photoluminescence measurement of a sample, in accordancewith one embodiment of the present invention.

FIG. 1I illustrates a simplified schematic view of a system for defectdetection and photoluminescence measurement of a sample, in accordancewith one embodiment of the present invention.

FIG. 1J illustrates a set of spectral integration bins superposed on aphotoluminescent spectrum, in accordance with one embodiment of thepresent invention.

FIG. 2 is process flow diagram illustrating steps performed in a methodfor defect detection and photoluminescence measurement of a sample, inaccordance with an embodiment of the present invention.

FIG. 3 is process flow diagram illustrating steps performed in a methodfor defect detection and photoluminescence measurement of a sample, inaccordance with an embodiment of the present invention.

FIG. 4 is process flow diagram illustrating steps performed in a methodfor defect detection and photoluminescence measurement of a sample, inaccordance with an embodiment of the present invention.

FIG. 5 is process flow diagram illustrating steps performed in a methodfor defect detection and photoluminescence measurement of a sample, inaccordance with an embodiment of the present invention.

FIG. 6 is process flow diagram illustrating steps performed in a methodfor defect detection and photoluminescence measurement of a sample, inaccordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not necessarily restrictive of the invention as claimed. Theaccompanying drawings, which are incorporated in and constitute a partof the specification, illustrate embodiments of the invention andtogether with the general description, serve to explain the principlesof the invention. Reference will now be made in detail to the subjectmatter disclosed, which is illustrated in the accompanying drawings.

Referring generally to FIGS. 1A through 1J, a system for defectdetection and photoluminescence measurement and defect classification ona sample is described, in accordance with the present invention. It isnoted herein that certain crystalline defects, such as stacking faults(SFs) and basal plane dislocations (BPDs), present in semiconductordevice layers may produce a characteristic, albeit weak, luminescencesignature when excited with ultraviolet (UV) radiation (e.g., λ<385 nm).For example, stacking faults and basal plane defects associated with anepilayer of a wide-bandgap semiconductor power device (e.g., siliconcarbide based power device or gallium nitride based power device) mayemit photoluminescent light when illuminated with ultraviolet light. Inthe case of silicon carbide (SiC) based power devices, the ultravioletlight used to stimulate photoluminescence in the associated stackingfaults may roughly correspond to the 4H-SiC bandgap, a SiC polytypecommonly used for epilayer growth in the power device industry.

The various embodiments of system 100 (e.g., FIG. 1A) are directed, inpart, to an optical architecture and analysis procedure forsimultaneously performing photoluminescence (PL) mapping and defectdetection in a single platform (e.g., located in the same optical head).Specifically, in some embodiments, the present invention may allow forscattering and photoluminescence defect detection in substrate andepilayer portions of a given sample, such as a wide-bandgapsemiconductor based power device. In addition, the various embodimentsof the present invention may carry out scattering and photoluminescencedefect detection utilizing a spiral scanning inspection configuration(e.g., SURFSCAN system by KLA-TENCOR), which provides a fasterinspection process as decelerating, stopping, and directional changesare avoided.

The present invention provides for a tunable optical architecture,allowing a given sensor to detect a selected portion (i.e., spectralbin) of a given photoluminescence spectrum. As shown in FIG. 1B, asample containing multiple types of photoluminescing defects, such asstacking faults or basal plane defects, may generate a robustphotoluminescent spectrum 134 (e.g., see peaks 143 b-143 d of FIG. 1B)when excited with ultraviolet light. It is further noted that each typeof stacking fault may generate a characteristic photoluminescentspectral feature, such as a position of the photoluminescent peak. Forexample, as shown in FIG. 1B, a 4S-type stacking fault may display apeak at approximately 460 nm when excited with a 325 nm laser, a 2S-typestacking fault may display a peak at approximately 500 nm when excitedwith a 325 nm laser, and a bar-type stacking may display a peak atapproximately 420 nm when excited with a 325 nm laser. The presentinvention may independently measure selected spectral bands of thephotoluminescence spectrum associated with a given sample and based onthose measurements detect and/or classify the constituentphotoluminescent defects (e.g., classify types of stacking faults insample). It is noted herein that while the spectrum depicted in FIG. 1Bwas acquired with a 325 nm UV laser, the principles displayed in FIG. 1Bare also observed in spectrum generated with lasers of wavelengthsdifferent than 325 nm, such as, but not limited to, a 355 nm laser.

FIG. 1A illustrates a block diagram view of a system 100 for defectdetection and photoluminescence measurement of a sample, in accordancewith one embodiment of the present invention. In one embodiment, thesystem 100 includes an oblique-incidence radiation source 103 configuredto direct a beam of light 101 (e.g., laser beam) having anoblique-illumination wavelength λ_(O) onto a portion of the sample 104along a direction oblique to the surface of the sample 104. In anotherembodiment, the system 100 includes a normal-incidence radiation source102 configured to direct (via one or more optical elements) a beam oflight 110 (e.g., laser beam) having a normal-illumination wavelengthλ_(N) onto a portion of the sample 104 along a direction normal to thesurface of the sample 104. The oblique-incidence radiation source 103may emit light at any wavelength or range of wavelengths. Further, theoblique-incidence radiation source 103 may include any radiation sourceknown in the art. For example, the oblique-incidence radiation source103 may include, but is not limited to, a laser. In one embodiment, theoblique-incidence radiation source 103 may include a visible spectrumlaser. For example, the oblique-incidence radiation source 103 mayinclude, but is not limited to, a laser capable of emitting 405 nmlight. In an alternative embodiment, the oblique-incidence radiationsource 130 may include an ultraviolet spectrum laser.

In one embodiment, the system 100 may detect one or more defects on (orin) the surface of sample 104 by collecting and analyzing theoblique-incidence light that is elastically scattered by the one or moredefects. It is noted herein that the inclusion of the oblique-incidenceradiation source 103 and the corresponding detection sub-system allowsthe system 100 to operate in darkfield mode in at least someconfigurations of the present invention. It is further noted herein thatlight from the oblique-incidence source 103 aids in differentiationbetween pit defects and particle defects at the surface of the sample104 since particle defects display a stronger response to lightimpinging a substrate at an oblique angle than pit defects. As such,based on the measured response at the wavelength (or wavelength range)corresponding to the oblique-incidence light (e.g., 405 nm), one or moredefects at a sample surface may be classified as either a pit defect orparticle defect (e.g., classified via controller 141). An inspectionsystem and method suitable for differentiating between pit and particledefects is described in U.S. Pat. No. 6,201,601 to Vaez-Iravani et al.,issued Mar. 13, 2011, which is incorporated herein by reference in theentirety.

The normal-incidence radiation source 102 may emit light at anywavelength or range of wavelengths suitable for stimulating one or morephotoluminescence defects of the surface of sample 104, such as stackingfault defects located in the epilayers of the sample 104, to emitphotoluminescence light. For example, the normal-incidence radiation 110may include ultraviolet light. In one embodiment, the wavelength λ_(N)of the normal-incidence radiation 110 is less than the wavelength λ_(O)of the oblique-incidence radiation 101. For instance, thenormal-incidence radiation 110 may include ultraviolet light having awavelength of 355 nm, while the oblique-incidence radiation 101 may havea wavelength of 405 nm. Further, the normal-incidence radiation source102 may include any radiation source known in the art. For example, thenormal-incidence radiation source 102 may include, but is not limitedto, a laser. For instance, the normal-incidence radiation source 102 mayinclude, but is not limited to, an ultraviolet laser, such as anultraviolet continuous wave (CW) laser. For example, thenormal-incidence radiation source 102 may include, but is not limitedto, an ultraviolet laser capable of emitting 355 nm light. It is notedherein that 355 nm UV light is suitable for stimulatingphotoluminescence emission in stacking fault defects of a sample. It isfurther noted that the 355 nm wavelength is not a limitation and isprovided merely for illustration. It is recognized herein that differentwavelengths of light may be utilized by the normal-incidence lightsource 102 of the present invention to stimulate photoluminescenceemission in different types of photoluminescence defects.

In addition to the photoluminescence stimulating aspects describedpreviously herein, the system 100 may detect one or more defects on thesurface of sample 104 by collecting and analyzing the normal-incidencelight that is elastically scattered by one or more defects. In thisregard, the normal-incidence radiation source 102 and the correspondingdetection sub-system allow the system 100 to operate in darkfield modein at least some applications of the present invention.

It is noted herein that the terms “oblique-illumination wavelength” and“normal-illumination wavelength” are not limiting and are provided forillustration and clarity.

In one embodiment, the system 100 includes a set of collection optics106 configured to collect radiation from the sample 104. The collectionoptics 106 may include a collector 108 positioned above the sample 104and configured to collect light from the sample 104 and direct thecollected light to an input of the filter sub-system 115 and on to thevarious sensors of system 100.

In another embodiment, the radiation 112 emanating from the sample 104may include radiation elastically scattered by one or more defects ofthe sample 104 or photoluminescence radiation emitted by one or morephotoluminescing defects of the sample 104. For example, the collector108 is configured to collect the scattered and/or radiated light fromthe sample 104. For instance, after light 110 from the normal-incidenceradiation source 102 and/or light 101 from the oblique-incidence source103 impinges on the surface of the sample 104 (e.g., epilayers of sampleor substrate of sample 104), the light may be scattered or radiated viaphotoluminescence by one or more portions of the surface of the sample104 or defects located at the surface of the sample 104. In turn, thecollector 108 may collect the scattered or radiated light and transmitthe light to an input of the filter sub-system 115. While thedescription above describes the invention in the context of the geometrydepicted in FIG. 1A, the invention is not limited to such geometry orlight collection devices and methods. For instance, it is recognizedherein that system 100 may alternatively be configured to collect andmeasure light reflected from the sample 104.

The collector 108 of the collection optics 106 may include any opticalcollection device, such as a collector or objective, known in the art.For example, the collector 108 may include, but is not limited to, areverse Cassegrain-type reflective objective, as shown in FIG. 1A. It isnoted herein that the collection optics 106 are not limited to theconfiguration illustrated in FIG. 1A, which is provided merely forillustrative purposes. It is recognized herein that the collectionoptics 106 of system 100 may include a number of additional opticalelements (e.g., lenses, mirrors, filters, and the like) for collectingillumination being scattered or radiated from the sample 104 anddirecting that illumination to the filter sub-system 115 and detectionsub-system 137 of the present invention. An optical collectionsub-system suitable for collecting scattered or photoluminescentlyradiated light is described in U.S. patent application Ser. No.12/861,894, filed Aug. 24, 2010, which is incorporated above in theentirety. An additional optical collection sub-system suitable forcollecting scattered or photoluminescently radiated light is describedin U.S. Pat. No. 7,907,269 to Meeks, issued on Mar. 15, 2011, which isincorporated herein by reference in the entirety.

In another embodiment, the system 100 includes a filter sub-system 115.In one embodiment, the filter sub-system 115 is arranged to receiveradiation 114 collected by the set of collection optics 106. Forexample, radiation 114 from the sample 104, such as scattered light orradiated PL light, may be collected by collector 108 of the collectionoptics 106 and then transmitted to one or more portions of the filtersub-system 115. In another embodiment, the filter sub-system 115 isconfigured to separate the radiation 114 from the sample 104 into afirst portion of radiation including one or more wavelengths in thevisible or near-infrared spectrum associated with the light emitted bythe one or more photoluminescing defects of the sample 104, a secondportion of radiation including the normal-illumination wavelength λ_(N),and at least a third portion of radiation including theoblique-illumination wavelength λ_(O).

For the purposes of the present disclosure the terms “portion ofradiation” and “radiation within a spectral bin” may be usedinterchangeably. In this regard, the “first portion of radiationincluding one or more wavelengths in the visible or near-infraredspectrum” may be regarded as the “light within the visible ornear-infrared photoluminescence spectral bin.” Further, the “secondportion of radiation including the normal-illumination wavelength λ_(N)”may be regarded as the “light within the second scattering-normal bin”and the “third portion of radiation including the oblique-illuminationwavelength λ_(O)” may be regarded as the “the light within the thirdscatter-oblique bin.”

In one embodiment, the filter sub-system 115 includes one or moreoptical elements configured to separate the radiation 114 received fromthe sample 104 into a first portion 131 of radiation including one ormore wavelengths in the visible or near-infrared spectrum associatedwith the light emitted by the one or more photoluminescing defects ofthe sample 104, a second portion 133 of radiation including thenormal-illumination wavelength λ_(N), and at least a third portion 135of radiation including the oblique-illumination wavelength λ_(O).

In one embodiment, the system 100 includes a detection sub-system 137for measuring one or more characteristics of the first portion ofradiation 131 transmitted by the filter sub-system 115, one or morecharacteristics of the second portion of radiation 133 transmitted bythe filter sub-system 115 and the third portion of radiation 135transmitted by the filter sub-system 115. In one embodiment, thedetection sub-system 137 includes a first sensor 122 for measuring oneor more characteristics of the first portion of radiation 131transmitted by the filter sub-system 115, a second sensor 124 formeasuring one or more characteristics of the second portion 133 ofradiation transmitted by the filter sub-system 115, and at least a thirdsensor 126 for measuring one or more characteristics of the thirdportion 135 of radiation transmitted by the filter sub-system 115.

In one embodiment, the first optical element 116 may separate a firstspectral range of radiation 107 including the first portion of radiationfrom the radiation 114 received from the sample 104 and direct the firstspectral range of radiation 107 toward the first sensor 122 of thedetection sub-system 137.

In another embodiment, a second optical element 118 may receiveradiation 109 from the first optical element 116 that is not included inthe first spectral range of radiation 107. In another embodiment, thesecond optical element 118 may separate a second spectral range ofradiation 111, including the second portion of radiation from theradiation 109 received from the first optical element 116 and direct thesecond spectral range of radiation 111 toward the second sensor 124 ofthe detection sub-system 137.

In another embodiment, a third optical element 120 may receive radiation113 from the second optical element 118 not included in the firstspectral range of radiation 107 or the second spectral range ofradiation 111. In another embodiment, the third optical element 120 maydirect at least a portion of the third spectral range of radiation 113including the third portion of radiation toward the third sensor 126 ofthe detection sub-system 137.

It is noted that the optical elements of the filter sub-system 115 mayinclude any optical elements known in the art suitable for separatingthe light 114 received from the sample 104 into the first, second, andthird spectral ranges of radiation, as shown in FIG. 1A.

In one embodiment, the first optical element 116 may include a firstdichroic beam splitter, such as a long wave pass (LWP), suitable forseparating a first spectral range of radiation 107 including the firstportion of radiation from the radiation 114 received from the sample 104and directing the first spectral range of radiation 107 toward the firstsensor 122. In another embodiment, the second optical element 118 mayinclude a second dichroic beam splitter (e.g., LWP filter) suitable forreceiving radiation 109 from the first dichroic beam splitter 116,separating a second spectral range of radiation 111 including the secondportion of radiation from the radiation 109 received from the firstdichroic beam splitter 116 and directing the second spectral range ofradiation 111 toward the second sensor 124.

In another embodiment, the third optical element 120 may include amirror 120 for receiving radiation 113 from the second dichroic beamsplitter 118 and directing at least a portion of a third spectral rangeof radiation 113 including the third portion of radiation toward thethird sensor 126.

In an alternative embodiment, the third optical element 120 may beconfigured to at least separate a portion of a third spectral range ofradiation 113 including the third portion of radiation from theradiation received from the second optical element 118 and direct thethird spectral range of radiation 113 toward the third sensor 126, whiletransmitting radiation not included in the first spectral range ofradiation 107, the second spectral range of radiation 109 or the thirdspectral range of radiation 113 to one or more additional opticaldevices (not shown in FIG. 1A) located downstream from the opticalelement 120. In this example, the mirror 120 shown in FIG. 1A may bereplaced with a dichroic beam splitter (e.g., LWP filter), which servesto provide an additional access port to the light. For example, thelight passing through the dichroic beam splitter in this embodiment maybe couple to an external detector via an optical-fiber. In this regard,the system 100 may further analyze this portion of radiation. Forinstance, although not shown, the system 100 may include a spectrometerarranged to analyze light passing through the optical element 120. Aspectrometer system suitable for analyzing light not diverted to sensors122, 124 or 126 is described generally in U.S. application Ser. No.12/861,894, which is incorporated above by reference in the entirety.

In one embodiment, the filter sub-system 115 may be configured toselectively filter light 114 received from the sample 104 such that thesensors 122, 124, and 126 of the detection sub-system 137 each receive apre-selected band of light.

In another embodiment, the filter sub-system 115 includes a set ofnarrow band filters in order to allow the system 100 to selectivelymeasure the various radiation bands of interest, as shown in FIG. 1A. Inone embodiment, the filter sub-system 115 of system 100 includes a firstnarrow band pass filter 128. For example, the first narrow band passfilter 128 may be positioned between the first sensor 122 and the firstoptical element 116. In this regard, the first narrow band pass filter128 may receive the first spectral range of radiation 107 from the firstoptical element 116 and transmit the first portion of radiation 131 tothe first sensor 122, while blocking radiation not included in the firstportion of radiation.

In another embodiment, the filter sub-system 115 of system 100 includesa second narrow band pass filter 130. For example, the narrow band passfilter 130 may be positioned between the second sensor 124 and thesecond optical element 118. In this regard, the second narrow band passfilter 130 may receive the second spectral range of radiation 111 andtransmit the second portion of radiation 133 to the second sensor 124,while blocking radiation not included in the second portion of radiation133.

In another embodiment, the filter sub-system 115 of system 100 includesa third narrow band pass filter 132. For example, the third narrow bandpass filter 132 may be positioned between the third sensor 126 and thethird optical element 120. In this regard, the third narrow band passfilter 132 may receive the third spectral range of radiation 113 andtransmit the third portion of radiation 135 to the third sensor 126,while blocking radiation not included in the third portion of radiation135.

While system 100 has been described in the context of using narrow bandfilters and LWP filters to direct the various bands of light to thecorresponding sensors, the present invention is not limited to thisoptical architecture. Rather, the optical configuration depicted withrespect to system 100 is provided merely for illustration and is notlimiting. It is anticipated that a variety of analogous opticalconfigurations may be implemented in order to separate radiation 114from the sample 104 into the desired spectral bands of the presentinvention. For example, the system 100 may include an opticalconfiguration equipped with one or more spectrometers. By way of anotherexample, the system 100 may include an optical configuration equippedwith one or more diffractive elements (e.g., diffraction grating)optically coupled to a photodetector. By way of another example, thesystem 100 may include an optical configuration equipped with one ormore dispersive elements (e.g., prism) optically coupled to aphotodetector.

In one embodiment, the filter sub-system 115 and the sensor 122 may bearranged such that the first sensor 122 receives light correspondingwith visible PL light or near-IR light radiated from one or more PLdefects of the sample 104. In one embodiment, the normal-incidencesource 102 may illuminate one or more portions of the sample 104 withultraviolet light, such as laser light having a wavelength ofapproximately 355 nm. In response, PL defects present in the epilayersof the sample may absorb the UV light and then radiate light in thevisible and/or near-IR spectrum. Then, the first narrow bandpass filter128 may transmit light of a selected band, such as light between 417 and900 nm, to the first sensor 122, allowing the system 100 to detectstacking faults in the visible and/or near IR spectrum. As describedfurther herein, the spectral location and width of the selected band maybe a function of anticipated PL features present in a given sample 104,allowing the system 100 to be tuned to a particular PL detectionscenario.

In another embodiment, the filter sub-system 115 and the sensor 124 maybe arranged such that the second sensor 124 receives light includingnormal-incidence wavelength light λ_(N) scattered by defects and/or thesample surface. In one embodiment, the normal-incidence source 102 mayilluminate one or more portions of the sample 104 with normal-incidencelight 110 of wavelength λ_(N) (e.g., ultraviolet light, such as 355 nmlight). In response, one or more defects or portions of the sample 104surface may scatter or reflect the λ_(N) light. Then, the second narrowbandpass filter 130 may transmit light of a selected band, such as awavelength band including light emitted by the λ_(N)-source, to thesecond sensor 124. For example, in the case where the normal-incidencesource 102 is a UV source, emitting light at 355 nm, the second narrowbandpass filter 130 may be configured to transmit light in the range350-360 nm.

In another embodiment, the filter sub-system 115 and the third sensor126 may be arranged such that the third sensor 126 receives lightincluding oblique-incidence wavelength light λ_(O) scattered by defectsand/or the sample 104 surface. In one embodiment, the oblique-incidencesource 103 may illuminate one or more portions of the sample 104 withoblique-incidence light 101 of wavelength λ_(O) (e.g., 405 nm light). Inresponse, one or more defects or portions of the sample 104 surface mayscatter or reflect the λ_(O) light. Then, the third narrow bandpassfilter 132 may transmit light of a selected band, such as a wavelengthband including light emitted by the λ_(O)-source, to the third sensor126. For example, in the case where the oblique-incidence source 103emits light at 405 nm, the third narrow bandpass filter 132 may beconfigured to transmit light in the range 400-410 nm, allowing thesystem 100 to detect stacking faults in the UV spectrum. By way ofanother example, in the case where the oblique-incidence source 103emits light at 405 nm, the third narrow bandpass filter 132 may beconfigured to transmit light in the range 370-410 nm, allowing thesystem 100 to detect stacking faults and basal plane dislocation defectsin the near-UV (NUV) spectrum.

It is noted herein that the implementation of the filter sub-system 115and detection sub-system 137 described above allows the system 100 toisolate various signal contributions from the illuminated sample 104. Inthis regard, it is possible to simultaneously measure the scattering ofoblique-incidence illumination, the scattering of normal-incidenceillumination and radiated PL light, stimulated by a UV source in amanner allowing for the isolated measurement of each. In addition, theconfiguration described above aids in avoiding cross-talk for thescattered oblique-incidence light and the scattered normal-incidencelight (i.e., the coupling of undesired bands into low levels ofscattered light).

It is noted herein that the sensors 122, 124, and 126 (and the sensorsof embodiments described further herein) may include any type of lightsensor architecture known in the art. For example, the sensors of system100 may include, but are not limited to, photomultiplier tubes (PMTs).In an alternative embodiment, the sensors of the system 100 may include,but are not limited to, photodiodes (e.g., avalanche photodiodes).

In one embodiment, the system 100 includes a controller 141communicatively coupled to one or more portions of the detectionsub-system 137, as show in FIGS. 1A and 1D. In one embodiment, thecontroller 141 is communicatively coupled to the first sensor 122, thesecond sensor 124, and the third sensor 126 of the detection sub-system137. In this regard, the controller 141 (e.g., one or more processors ofthe controller 141) may receive measurement results from the firstsensors 122, the second sensor 124, and the third sensor 126.

In one embodiment, the controller 141 may receive a signal indicative ofone or more characteristics (e.g., signal intensity) of the firstportion of radiation, corresponding to light falling within the definedvisible or near-infrared spectral bin (e.g., 417-900 nm), whichincludes, at least in part, the visible and/or near-infrared lightemitted by the one or more photoluminescing defects of the sample 104.In another embodiment, the controller 141 may receive a signalindicative of one or more characteristics (e.g., signal intensity) ofthe second portion of radiation, corresponding to the light fallingwithin the defined scattering-normal spectral bin (e.g., 350-360 nm),which includes a wavelength range including the normal-incidencewavelength λ_(N) (e.g., 355 nm). In another embodiment, the controller141 may receive a signal indicative of one or more characteristics(e.g., signal intensity) of the third portion of radiation,corresponding to the light falling with the defined scattering-obliquespectral bin (e.g., 400-410 nm), which includes a wavelength rangeincluding the oblique-incidence wavelength λ_(O) (e.g., 405 nm).

In one embodiment, the controller 141 may detect one or more scatteringdefects based on the light measured by at least one of the second sensor124 and the third sensor 126. In one embodiment, the controller 141 mayanalyze the one or more signals of the second sensor 124 in order toidentify a defect, such as a particle, scattering λ_(N) light (e.g., 355nm). In another embodiment, although not shown, the system 100 may beconfigured to utilize the normal-incident channel (i.e.,normal-incidence radiation source 102 and second sensor 124 in UVspectrum) in reflection mode (i.e., brightfield channel) in order tomeasure specular reflectivity and one or more slope channels due to theopaque nature of various wide bandgap semiconductor materials (e.g., SiCand GaN) to UV light, yielding high image quality. In anotherembodiment, although not shown, the system 100 may be configured toutilize reflected light from the oblique-incident channel (e.g., 405 nmlight) to yield multi-channel signals such as, but not limited to,specular reflectivity, slope channel data, and phase channel data.

In one embodiment, the controller 141 may analyze the one or moresignals of the third sensor 126 in order to identify a defect, such as aparticle, which scatters light having a wavelength of λ_(O) (e.g., 405nm). In another embodiment, system 100 may utilize oblique reflectedlight of wavelength λ_(O) to yield multichannel signals, such as, butnot limited to, specular reflectivity, slope and phase channels.

In another embodiment, the system 100 may include one or more confocalapertures (not shown) in order to aid in separating backside scatterfrom frontside scatter in cases where the illumination wavelength (e.g.,405 nm) is transparent to the given wide bandgap material (e.g., SiC) ofthe sample 104. The application of one or more confocal apertures isdescribed generally in U.S. Pat. No. 7,907,269 to Meeks, filed on Jun.24, 2010, which is incorporated herein by reference in the entirety.

In another embodiment, the controller 141 may detect one or morephotoluminescence defects based on at least one of the one or morecharacteristics, such as one or more signal characteristics (e.g.,signal intensity), measured by the first sensor 122, the one or morecharacteristics measured by the second sensor 124, and the one or morecharacteristics measured by the third sensor 126. In another embodiment,the controller 141 may detect one or more photoluminescence defects bycomparing the one or more characteristics from at least one of the firstsensor 122, the second sensor 124, and the third sensor 126 in an areaof the sample 104 absent of photoluminescing defects to a signal from atleast one of the first sensor 122, the second sensor 124, and the thirdsensor 126 acquired from a measured region of the sample 104. In oneembodiment, in obtaining a measurement of signal intensity of an areavoid of photoluminescence defects, one or more of the sensors 122, 124,126 may acquire detection data from areas known to be void ofphotoluminescence defects. Curve 143 a, depicted in FIG. 1B, is a set ofphotoluminescence intensity versus wavelength curves of a region of asample 104 void of photoluminescence defects. It is noted herein thatthis photoluminescence-defect-free curve 143 a may then be compared todata acquired from additional regions of the sample 104 in order toidentify one or more photoluminescence defects.

In another embodiment, the controller 141 may map the detected one ormore photoluminescence defects based on at least one of the one or morecharacteristics measured by the first sensor 122, the one or morecharacteristics measured by the second sensor 124, and the one or morecharacteristics measured by the third sensor 126 along with the knownposition of the detected one or more photoluminescence defects. In thisregard, a two-dimensional map may be generated by the detector, wherebythe spectral signature measured by each detector is plotted at a givenmeasurement position. In this manner, a topographical map displaying themapping of multiple spectral bands may be displayed. In alternativeembodiment, the controller 141 may selectively display only a portion ofthe multiple spectral bands. In this regard, the controller 141 maydisplay a map of features measured in a single spectral band or displaya map of features measured in two or more spectral bands.

In another embodiment, the controller 141 may classify the detected oneor more photoluminescence defects based on at least one of the one ormore characteristics, such as spectral characteristics (e.g., spectrum,intensity, spectral position of one or more peaks) measured by the firstsensor 122, the one or more characteristics measured by the secondsensor 124, and the one or more characteristics measured by the thirdsensor 126. It is noted herein that a particular type ofphotoluminescence defect (or defects) will display a characteristicspectrum, as previously described and shown by curves 143 b-143 d ofFIG. 1B. By measuring the intensity of a particular spectral bin, suchas spectral bin 145 and/or spectral bin 147 shown in FIG. 1B, thecontroller 141 may determine the type of photoluminescence defect beingmeasured. For example, the controller 141 may compare the measured anddetected results previously described herein to a look-up table in orderto identify the type of one or more detected photoluminescence defects.For instance, a look-up table containing information that correlatesvarious types of photoluminescence defects, such as stacking faultdefects (e.g., bar-shaped stacking faults, 2SSF stacking faults, 4SSFstacking faults, and the like), to a corresponding photoluminescencespectrum may be built up by the system 100 (or an additional system) andstored in memory. Photoluminescence spectra associated with particularstacking faults is generally described in Feng et al., “Characterizationof Stacking Faults in 4H-SiC Epilayers by Room-TemperatureMicrophotoluminescence Mapping,” Applied Physics Letters, Vol. 92, Issue22 (2008), which is incorporated herein by reference in the entirety. Itis noted herein that effective classification is achieved in settingswith additional sensors, whereby each of the sensors are matched to agiven spectral bin corresponding to a known spectral signature for agiven stacking fault time. This approach is discussed in greater detailfurther herein.

In one embodiment, the spectral bin 145 may represent the UV-to-Visiblephotoluminescence integration band that is produced by stimulatingphotoluminescence with a 355 nm laser and detecting photoluminescencelight using a 420-700 nm spectral band, effectuated with the filtersub-system 115 and detection sub-system 137 as described previouslyherein. In another embodiment, as shown in FIG. 1B, the spectral bin 147may represent the UV-to-UV photoluminescence integration band that isproduced by stimulating photoluminescence with a 355 nm laser anddetecting photoluminescence light using a 400-410 nm spectral band,effectuated with the filter sub-system 115 and detection sub-system 137as described previously herein. In another embodiment, as shown in FIG.1E, the spectral bin 147 may represent a UV-to-NUV photoluminescenceintegration band that is produced by stimulating photoluminescence witha 355 nm laser and detecting photoluminescence light using a broaderband, such as, but not limited to, a 370-410 nm spectral band,effectuated with the filter sub-system 115 and detection sub-system 137as described previously herein. In additional embodiments, it is notedthat the spectral bin 147 may correspond to spectral ranges such as, butnot limited to, 370-400 nm for the purposes of detecting NUV emittingdefects. It is noted herein that the spectral binning configuration ofFIG. 1E is suitable for detecting both stacking faults and basal planedislocations.

It is noted herein that the visible/NIR detection using spectral bin 145may correspond to a ‘positive’ contrast, or ‘bright’ contrast, detectionprocess, whereby the intensities of the characteristic peaks in thephotoluminescence spectrum are larger than the background intensitycorresponding with the photoluminescence-defect-free curve 143 a. Incontrast, the NUV detection using spectral bin 147 (e.g., correspondingwith a band of 370-410 nm and the like) may correspond with a ‘negative’contrast, or ‘dark’ contrast, detection process, whereby the intensitiesof the characteristic peaks in the photoluminescence spectrum aresmaller than the background intensity corresponding with thephotoluminescence-defect-free curve 143 a.

FIG. 1F illustrates a pair of photoluminescence inspection imagesdepicting imagery data obtained utilizing the NUV-based dark contrastdetection scheme and the visible-based bright contrast detection scheme,in accordance with one or more embodiments of the present invention.Image 170 depicts imagery data obtained utilizing a spectral bincorresponding to the NUV band described above (e.g., 370-410 nm). Asshown in image 170, the stacking fault 172 and basal plane dislocation174 both display a high level of negative contrast. The stacking faultportion 176 of the split basal plane dislocation, however, displaysfainter negative contrast. Image 178 depicts imagery data obtainedutilizing a spectral bin corresponding to the visible band describedabove (e.g., 420-700 nm). As shown in image 178, the stacking fault 172and the stacking fault portion 176 of the split basal plane dislocationboth display relatively strong positive contrast. However, the basalplane dislocation 174 displays no measurable bright contrast in image178. It is noted herein that the basal plane dislocation 174 is alsoknown to be faintly bright in the NIR band, such as 750-900 nm.

In an alternative embodiment, as illustrated in FIG. 1D, the controller141 is configured to selectably deactivate the oblique-incidenceradiation source 103. In one embodiment, the second sensor 124, whichmay detect radiation in a range at least including light of λ_(O), maybe utilized to detect photoluminescence radiation emitted by one or morephotoluminescent defects. In a further embodiment, the controller 141may deactivate the oblique-incidence radiation source 103 prior to thephotoluminescence measurement by the second sensor 124. For example, inthe case where λ_(O)=405 nm and the second sensor 124 is configured todetect radiation in the band 400-410 nm, the controller 141 maydeactivate the oblique-incidence radiation source 103 in order to samplephotoluminescence light within the 400-410 nm band, which was generatedvia the stimulation by the 355 nm ultraviolet normal-incidence radiationsource 102. It is recognized herein that this detection scenario (i.e.,detecting defect scattered λ_(O) radiation and detectingphotoluminescence radiation in the same range) may be carried oututilizing two inspection passes of the sample.

In one embodiment, the controller 141 includes one or more processors(not shown) and a non-transitory storage medium (i.e., memory medium).In this regard, the storage medium of the controller 141 (or any otherstorage medium) contains program instructions configured to cause theone or more processors of controller 141 to carry out any of the varioussteps described through the present disclosure. For the purposes of thepresent disclosure the term “processor” may be broadly defined toencompass any processor or logic element(s) having processingcapabilities, which execute instructions from a memory medium. In thissense, the one or more processors of controller 141 may include anymicroprocessor-type device configured to execute software algorithmsand/or instructions. In one embodiment, the one or more processors mayconsist of a desktop computer or other computer system (e.g., networkedcomputer) configured to execute a program configured to execute thecomputational/data processing steps described throughout the presentdisclosure. It should be recognized that the steps described throughoutthe present disclosure may be carried out by a single computer system,multiple computer systems, or a multi-core processor. Moreover,different subsystems of the system 100, such as a display device or auser interface device (not shown), may include a processor or logicelements suitable for carrying out at least a portion of the stepsdescribed above. Therefore, the above description should not beinterpreted as a limitation on the present invention, but rather merelyan illustration.

In one embodiment, the system 100 includes a sample stage assembly 105configured to secure the sample 104 and selectively actuate the sample104 in order to perform a scanning process with at least theoblique-incidence radiation source 103 and the normal-incidenceradiation source 102. In this regard, the sample stage 105 and/or theoptical head containing the oblique-incidence radiation source 103 andthe normal-incidence radiation source 102 may be selectively actuated,thereby scanning the sample 104 relative to the incident light beams 101and 110.

In one embodiment, the sample stage assembly 105 of system 100 includesa rotational sample stage assembly configured to secure the sample 104and selectively rotate the sample 104. In one embodiment, the rotationalsample stage assembly includes a sample chuck (not shown) for securingthe sample 104. For example, the sample chuck may include, but is notlimited to, a vacuum chuck. In another embodiment, the rotational samplestage assembly includes a sample spindle (not shown) configured toselectively rotate the sample 104. For example, the sample spindle mayrotate the sample 104 at a selected rotational speed about an axisperpendicular to the surface of the sample 104. In another embodiment,the spindle may selectively rotate (or stop rotation) of the sample inresponse to an associated controller or control system (e.g., controller141).

In one embodiment, a rotational sample stage of system 100 is configuredto carry out a spiral scanning process. In one embodiment a rotationalsample stage of system 100 may rotate the sample 104 at a selectedrotational speed, while an optical head including the oblique-incidencesource 103 and the normal incidence radiation source 102 is translatedalong a selected linear direction (e.g., along a radial line of thesample 104). For example, the optical head may be coupled to a linearstage suitable for translating the optical head along a selected lineardirection. The combined motion of the rotation of the sample 104 and thelinear motion of the oblique-incidence radiation source 103 and thenormal incidence radiation source 102 generates a spiral scanningpattern 149, as shown in FIG. 1C. In this regard, the sample 104, suchas a SiC wafer, may be rapidly rotated (e.g., 5000 RPM) under theoptical head (including oblique-incidence radiation source 102 andnormal incidence radiation source 103) and moved slowly along one radiusof the sample 104 with a selected track pitch (e.g., 4 μm). Forinstance, the optical head may be moved along a radial direction fromthe edge of the sample 104 to the center of the sample 104.

It is noted herein that the spiral scanning technique provides for arelatively fast scanning process as no time is required fordecelerating, accelerating, stopping or changing directions, which isrequired in most X-Y scanning architectures (e.g., scanning, swathing,or move-acquire-measure configurations). A spiral scanning architecturesuitable for implementing the spiral scanning procedure described hereinis described generally in U.S. Pat. No. 6,201,601 to Vaez-Iravani etal., filed on Sep. 19, 1997, which is incorporated herein in theentirety.

In an alternative embodiment, the sample stage assembly 105 of system100 includes a linear stage assembly (not shown) configured to securethe sample 104 and selectively translate the sample 104 along at least afirst direction (e.g., X-direction) and a second direction (e.g.,Y-direction) perpendicular to the first direction in order to perform anX-Y scanning process with at least the oblique-incidence radiationsource 103 and the normal-incidence radiation source 102.

FIG. 1G illustrates a block diagram view of system 100, in accordancewith an alternative embodiment of the present invention. It is notedherein that the embodiments and examples described previously hereinwith respect to system 100 should be interpreted to extend to theembodiments of system 100 depicted in FIG. 1G unless otherwise noted.

It is further noted herein that the embodiment depicted in FIG. 1Gserves to provide an additional ultraviolet detection band, allowingsystem 100 to simultaneously detect defect scattered light at λ_(O)(e.g., light generated by oblique-incidence light source 103) as well asultraviolet photoluminescent light generated by the stimulation of oneor more photoluminescent defects by the normal-incidence light source102.

In one embodiment, the detection sub-system 137 includes a fourth sensor142 for measuring one or more characteristics of a fourth portion 139 ofradiation transmitted by the filter sub-system 115. In one embodiment,the fourth portion 139 of radiation corresponds to ultraviolet radiationhaving a wavelength less than the smallest wavelength of the thirdportion of radiation 135. For example, in the case where the thirdsensor 126 measures oblique scattered light across a band of 400-410 nm(e.g., λ_(O)=405 nm), the fourth sensor 142 may be configured to measureradiation below 400 nm. For instance, the fourth sensor 142 may sampleradiation in the band 370-400 nm, which may correspond to at least aportion of the ultraviolet band corresponding to ultraviolet lightgenerated by the ultraviolet excitation of one or more photoluminescentdefects, which can be observed in the photoluminescence spectral data inFIG. 1B.

In another embodiment, the third optical element 120 of the filtersub-system 115 is configured to receive radiation from the secondoptical element 118 not included in the first spectral range ofradiation 107 or the second spectral range of radiation 111. Further,the third optical element 120 is configured to at least separate aportion of a third spectral range of radiation 117 including the thirdportion of radiation 135 from the radiation received from the secondoptical element 118 and direct the third spectral range of radiation 117toward the third sensor 126. In addition, the third optical element 120is further configured to transmit radiation not included in the firstspectral range of radiation 107, the second spectral range of radiation111 or the third spectral range of radiation 117 toward the fourthsensor 142 in a fourth spectral range of radiation 119 including afourth portion of radiation 139. In another embodiment, the thirdoptical element 120 of the filter sub-system 115 may include, but is notlimited to, a dichroic optical element (e.g., LWP filter).

In another embodiment, the filter sub-system 115 may include a fourthnarrow pass filter 144. In one embodiment, the fourth narrow pass filter144 is positioned between the fourth sensor 142 and the third opticalelement 120 and is configured to receive the fourth spectral range ofradiation 119 and transmit the fourth portion 139 of radiation, such asultraviolet photoluminescent light (e.g., 370-400 nm) to the fourthsensor 142 and block radiation not included in the fourth portion 139 ofradiation.

FIG. 1H illustrates a block diagram view of system 100, in accordancewith an alternative embodiment of the present invention. It is notedherein that the embodiments and examples described previously hereinwith respect to system 100 should be interpreted to extend to theembodiments of system 100 depicted in FIG. 1H unless otherwise noted.

It is further noted herein that the embodiment depicted in FIG. 1Hserves to provide a detection scenario without the oblique-incidenceradiation source 103 described previously herein. In this embodiment,system 100 detects scattered light only via the second sensor 124, whichis configured to measure one or more characteristics of the secondportion 133 of radiation (e.g., 350-360 nm) transmitted by the filtersub-system 115. It is further noted that in the context of thisembodiment the third sensor of this embodiment 142 is substantiallysimilar to the fourth sensor 142 of the embodiment described previouslyherein in FIG. 1G. In this regard, the third sensor 142 of FIG. 1H maymeasure one or more characteristics of a third portion 139 of radiationtransmitted by the filter sub-system 115. In one embodiment, the thirdportion 139 of radiation corresponds to ultraviolet radiation having awavelength larger than the largest wavelength of the second portion ofradiation 133. For example, in the case where the second sensor 124measures normal scattered light across a band of 350-360 nm (e.g.,λ_(N)=355 nm), the third sensor 142 may be configured to measureradiation above 360 nm. For instance, the third sensor 142 may sampleradiation in the band 370-410 nm, which may correspond to at least aportion of the ultraviolet band corresponding to ultraviolet lightgenerated by the ultraviolet excitation of one or more photoluminescentdefects, which can be observed in the photoluminescence spectral data inFIG. 1B.

In another embodiment, optical element 120 of the system 100 may includea mirror for directing the third spectral range of radiation 113 towardthe third sensor 142 for detecting UV photoluminescent radiation.

FIG. 1I illustrates a block diagram view of system 100, in accordancewith an alternative embodiment of the present invention. It is notedherein that the embodiments and examples described previously hereinwith respect to system 100 should be interpreted to extend to theembodiments of system 100 depicted in FIG. 1I unless otherwise noted.

It is further noted herein that the embodiment depicted in FIG. 1Iserves to provide a number of photoluminescence spectral bins, eachmatched to a particular spectral signature of a type of stacking fault(e.g., bar-shaped stacking faults, 2S stacking faults and 4S stackingfaults). This configuration further provides for the classification ofstacking faults, in real-time or near-real-time.

Further, the embodiment depicted in FIG. 1I may achieve the type ofspectral segmentation depicted in FIG. 1J below, which serves to isolatethe characteristic photoluminescence bands into several distinctphotoluminescence spectral bins. It is noted herein that some level ofcross-talk may exist given the broad photoluminescent lines for eachdefect type in spectrum 161. It is further recognized, however, that agood balance between total signal and crosstalk reduction may beachieved by choosing the photoluminescence bins to roughly correspond tothe full width half maximum (FWHM) of each radiative recombination linefor each stacking fault type.

In one embodiment, the system 100 may be configured without theoblique-incidence radiation source 103 and corresponding sensor 126 andfilter 132. In another embodiment, the controller 141 of system 100 mayselectively activate and deactivate the oblique-incidence radiationsource 103, as described previously herein. In yet another embodiment,the system 100 may include the oblique-incidence radiation source 103,as described previously herein. It is noted herein that the followingdescription is provided in the context of the oblique-incidenceradiation source 103 being including in system 100. It is further noted,however, that this is not a limitation and the system 100 may beembodied without the oblique-incidence radiation source 103.

As described previously herein, the filter sub-system 115 of system 100is configured to receive at least a portion of the radiation collectedby the set of collection optics 106.

In the case where the oblique-incidence radiation source 103 is present,the filter sub-system 115 is further configured to separate theradiation into a portion 111 of radiation including thenormal-illumination wavelength λ_(N) and an additional portion 117 ofradiation including the oblique-illumination wavelength λ_(O), asdescribed previously herein.

In another embodiment, the filter sub-system 115 is configured toseparate the radiation 114 from the sample 104 into a plurality ofportions of photoluminescent radiation. In another embodiment, eachportion includes one or more wavelengths in a different spectral rangeof the radiation emitted by the one or more photoluminescing defects ofthe sample 104.

By way of example, the detection sub-system 137 may include, but is notlimited to, a first PL sensor 146 for measuring one or morecharacteristics (e.g., intensity) of a first portion of PL radiationtransmitted by the filter sub-system 115, a second PL sensor 150 formeasuring one or more characteristics of a second portion of PLradiation transmitted by the filter sub-system 115, a third PL sensor148 for receiving a third portion of PL radiation transmitted by thefilter sub-system 115 and a fourth PL sensor 142 for receiving a fourthportion of PL radiation transmitted through the filter sub-system 115.

In another embodiment, as described previously herein, the detectionsub-system 137 may further include a normal-scattering sensor 124 forreceiving λ_(N) radiation scattered from one or more defects of thesample 104 and an oblique-scattering sensor 126 for receiving λ_(O)radiation scattered from one or more defects of the sample 104.

In one embodiment, each of the sensors described above may correspondwith a particular spectral bin. In one embodiment, filter sub-system 115includes a plurality of optical elements and a plurality of narrow bandfilters in order to separate the radiation received from the sample intoa plurality of spectral bins.

In one embodiment, the plurality of optical elements may include, but isnot limited to, optical elements 116, 118, 140, 152, and 154. Forexample, each of the optical elements 116, 118, 140, 152, and 154 mayinclude, but are not limited to, a dichroic beam splitter (e.g., LWPfilter), as described previously herein. It is recognized herein thateach of the optical elements 116, 118, 140, 152, and 154 may serve todirect a given spectral range of radiation including a selected spectralband toward the corresponding sensor. In another embodiment, theplurality of narrow band filters may include, but is not limited tonarrow band filters 130, 132, 156, 158, 159, and 144. It is recognizedherein that each of the narrow band filters may serve to define a givenspectral bin of the plurality of spectral bins by transmitting lightincluded in the given spectral bin and blocking light outside the givenspectral bin.

In one embodiment, the first PL sensor 146 is configured to receiveradiation in a spectral band of 480-520 nm from the first narrow bandfilter 156. In another embodiment, the second PL sensor 150 isconfigured to receive radiation in a spectral band of 440-470 nm fromthe narrow band filter 159. In another embodiment, the third PL sensor148 is configured to receive radiation in a spectral band of 410-435 nmfrom the narrow band filter 158. In one embodiment, the fourth PL sensor142 is configured to receive radiation in a spectral band of 370-400 nmfrom the narrow band filter 144. In another embodiment, thenormal-scattering sensor 124 may receive radiation in a spectral band of350-360 nm from the narrow band filter 130, while the oblique-scattersensor 126 may receive radiation in a spectral band of 400-410 nm fromthe narrow band filter 132.

In one embodiment, the optical elements and the plurality of narrow bandfilters are arranged to define the plurality of spectral bins accordingto a set of anticipated spectral characteristics of one or morephotoluminescent defects of the sample. In another embodiment, theplurality of optical elements and the plurality of narrow band filtersare arranged to substantially match the full width half maximum (FWHM)values to a set of corresponding intensity peaks of a photoluminescentspectrum 161. In one embodiment, as shown in FIG. 1J, a first spectralbin 162 (defined by filter 156 and sensor 146) may be matched to a firstphotoluminescence peak 163 (e.g., FWHM) indicative of the presence of afirst type of stacking fault (e.g., 2S stacking faults). In anotherembodiment, as shown in FIG. 1H, a second spectral bin 164 (defined byfilter 159 and sensor 150) may be matched to a second photoluminescencepeak 165 (e.g., FWHM) indicative of the presence of a second type ofstacking fault (e.g., 4S stacking faults). In another embodiment, asshown in FIG. 1J, a third spectral bin 166 (defined by filter 158 andsensor 148) may be matched to a third photoluminescence peak 167 (e.g.,FWHM) indicative of the presence of a third type of stacking fault(e.g., bar-type stacking faults).

In another embodiment, as shown in FIG. 1J, a fourth spectral bin 168(defined by filter 144 and sensor 142) may be matched to one or morefourth photoluminescence peaks 169 (e.g., FWHM). In the case of thephotoluminescent spectrum 161 of FIG. 1J, the spectral bin 168 acts tomeasure a set of broad photoluminescent peaks indicative of the presenceof each type of stacking fault defect described above.

In another embodiment, the control system 141 of system 100 may detectone or more photoluminescence defects based on the light detected byeach of the plurality of sensors. In one embodiment, the control system141 may detect the photoluminescence defects by comparing a signal fromat least one of the plurality of sensors in an area of the sample 104absent of photoluminescing defects to a signal from at least one of theplurality of sensors acquired from a measured region of the sample 104.In this regard, each stacking fault type may be detected in dedicatedspectral bins, each coupled to a dedicated sensor (e.g., PMT).

In another embodiment, the controller 141 may classify the one or moredetected photoluminescence defects based on one or more signals measuredby each of the plurality of sensors. In this regard, the controller 141may classify each stacking fault defect based on the presence ofphotoluminescent signature wavelengths. It is noted herein that theimplementation of the spectral bins of the present invention allows forfast and efficient photoluminescent defect classification in settingswhere the given defect(s) is too small for adequate identification viashape algorithms. It is understood that when the size of thephotoluminescent-only defect is large enough to be properly sampled andrepresented in imagery data the system may further apply one or moreshape identification algorithms to classify the given defect (e.g.,triangle defect, bar defect and the like). It is further recognized thatthe embodiment depicted in FIG. 1I is not limited to the spectral binsexplicitly noted above. Rather, the spectral bins discussed in thepresent disclosure have been provided merely for illustrative purposes.It is anticipated that additional spectral bin scenarios may beapplicable within the scope of the present invention. For example,rather than three individual spectral bins (as shown in FIGS. 1I and1J), the system 100 may carry out the classification process utilizingadditional spectral bins. For instance, utilizing additional spectralbins, the controller 141 may classify defects based on the fact that atriangle stacking fault should have strong back level swing, whereas abar-shaped stacking fault may have strong black level signature, and atthe same time, a reduced white level signature. This difference inrelative signal variations may be used for stacking fault classificationusing photoluminescence.

While the foregoing description has focused on oblique channel andnormal channel photoluminescence defect (e.g., SF defect and basal planedislocations) and scattering defect detection, it is recognized hereinthat the system 100 of the present invention may utilize additionalarchitectures and configurations during implementation. In someembodiments, the system 100 may be equipped with autofocusing devicesfor carrying out an autofocus routine during inspection and detection ofscattering defect and photoluminescence defects. In other embodiments,the system 100 of the present invention may be equipped with powercontrol devices and systems for controlling the power of the lightsources (e.g., oblique-incidence source 103 and normal-incidence source102). For instance, the one or more power control devices may be used tocontrol the power of light incident on the sample 104 for calibration orother purposes.

In other embodiments, the system 100 may include one or more obliquechannels configured to measure reflected light from the sample 104. Forinstance, the system 100 may include additional light sources, opticalfocusing and control elements, and detection devices configured formeasuring specular reflection of the sample 104, one or more slopechannels, and/or one or more phase channels.

In other embodiments, the controller 141 of system 100 may retrievesignals from any of the various channels of the system 100 in order toclassify one or more defects. For example, the controller 141 mayreceive signals from one or more of the following channels:oblique-incidence channel, normal-incidence channel, specular reflectionchannel, slope channel, phase channel and the like. Then, based on ananalysis of the defect signatures in the data from one or more of thesechannels the controller 141 may classify a measured defect. Forinstance, the controller 141 may compare an image taken via a firstchannel in a first contrast mode and then compare that image to an imagetaken via a second channel (or an Nth channel) in an Nth contrast modein order to classify one or more photoluminescence defects (e.g., SFdefects or basal plane dislocations) of sample 104.

FIG. 2 illustrates a process flow diagram 200 depicting a method fordefect detection and photoluminescence measurement of a sample. In step202, a beam of oblique-illumination wavelength light is directed onto aportion of the sample along a direction oblique to the surface of thesample. In step 204, a beam of normal-illumination wavelength light isdirected onto a portion of the sample along a direction substantiallynormal to the surface of the sample. In one embodiment, the beam oflight of the normal-illumination wavelength is suitable for causing oneor more photoluminescing defects of the sample to emit photoluminescentlight. In step 206, radiation from the sample is collected. In oneembodiment, the radiation from the sample including at least one ofradiation elastically scattered by one or more defects of the sample orphotoluminescence radiation emitted by the one or more photoluminescingdefects of the sample. In step 208, the radiation from the sample isseparated into a first portion of radiation including one or morewavelengths in the visible spectrum associated with the light emitted bythe one or more photoluminescing defects of the sample, a second portionof radiation including the normal-illumination wavelength light, and atleast a third portion of radiation including the oblique-illuminationwavelength light. In step 210, one or more characteristics of at leastone of the first portion of radiation, the second portion of radiationand the third portion of radiation are measured. In step 212, one ormore scattering defects are detected based on the measured one or morecharacteristics of at least one of the second portion of radiation andthe third portion of radiation. In step 214, one or morephotoluminescence defects are detected based on the measured one or morecharacteristics of at least one of the first portion of radiation, thesecond portion of radiation and the third portion of radiation bycomparing the one or more characteristics of at least one of the firstportion of radiation, the second portion of radiation and the thirdportion of radiation acquired from an area of the sample absent ofphotoluminescing defects to one or more characteristics of at least oneof the first portion of radiation, the second portion of radiation andthe third portion of radiation acquired from a measured region of thesample.

FIG. 3 illustrates a process flow diagram 300 depicting a method fordefect detection and photoluminescence measurement of a sample. In step302, a beam of oblique-illumination wavelength light is directed onto aportion of the sample along a direction oblique to the surface of thesample. In step 304, a beam of normal-illumination wavelength light isdirected along a direction substantially normal to the surface of thesample. In one embodiment, the beam of light of the normal-illuminationwavelength is suitable for causing one or more photoluminescing defectsof the sample to emit photoluminescent light. In step 306, radiationfrom the sample is collected. In one embodiment, the radiation from thesample including at least one of radiation elastically scattered by oneor more defects of the sample or photoluminescence radiation emitted bythe one or more photoluminescing defects of the sample. In step 308, theradiation from the sample is separated into a first portion of radiationincluding one or more wavelengths in the visible or near-infraredspectrum associated with the light emitted by the one or morephotoluminescing defects of the sample, a second portion of radiationincluding the normal-illumination wavelength, a third portion ofradiation including the oblique-illumination wavelength and at least afourth portion of radiation including one or more wavelengths in theultraviolet spectrum associated with the photoluminescent light emittedby the one or more photoluminescing defects of the sample. In step 310,one or more characteristics of at least one of the first portion ofradiation, one or more characteristics of the second portion ofradiation, one or more characteristics of the third portion of radiationand one or more characteristics of the fourth portion of radiation aremeasured. In step 312, one or more scattering defects are detected basedon the measured one or more characteristics of at least one of thesecond portion of radiation and the third portion of radiation. In step314, one or more photoluminescence defects are detected based on themeasured one or more characteristics of at least one of the firstportion of radiation, the second portion of radiation, the third portionof radiation and the fourth portion of radiation by comparing the one ormore characteristics of at least one of the first portion of radiation,the second portion of radiation, the third portion of radiation and thefourth portion of radiation acquired from an area of the sample absentof photoluminescing defects to one or more characteristics of at leastone of the first portion of radiation, the second portion of radiation,the third portion of radiation and the fourth portion of radiationacquired from a measured region of the sample.

FIG. 4 illustrates a process flow diagram 400 depicting a method fordefect detection and photoluminescence measurement of a sample. In step402, a beam of normal-illumination wavelength light is directed along adirection substantially normal to the surface of the sample. In oneembodiment, the beam of light of the normal-illumination wavelength issuitable for causing one or more photoluminescing defects of the sampleto emit photoluminescent light. In step 404, radiation from the sampleis collected. In one embodiment, the radiation from the sample includingat least one of radiation elastically scattered by one or more defectsof the sample or photoluminescence radiation emitted by the one or morephotoluminescing defects of the sample. In step 406, radiation from thesample is separated into a first portion of radiation including one ormore wavelengths in the visible or near-infrared spectrum associatedwith the light emitted by the one or more photoluminescing defects ofthe sample, a second portion of radiation including thenormal-illumination wavelength and at least a third portion of radiationincluding one or more wavelengths in the ultraviolet spectrum associatedwith the photoluminescent light emitted by the one or morephotoluminescing defects of the sample. In step 408, one or morecharacteristics of at least one of the first portion of radiation, oneor more characteristics of the second portion of radiation and one ormore characteristics of the third portion of radiation are measured. Instep 410, one or more scattering defects are detected based on themeasured one or more characteristics of at least one of the secondportion of radiation and the third portion of radiation. In step 412,one or more photoluminescence defects are detected based on the measuredone or more characteristics of at least one of the first portion ofradiation, the second portion of radiation, and the third portion ofradiation by comparing the one or more characteristics of at least oneof the first portion of radiation, the second portion of radiation andthe third portion of radiation acquired from an area of the sampleabsent of photoluminescing defects to one or more characteristics of atleast one of the first portion of radiation, the second portion ofradiation and the third portion of radiation acquired from a measuredregion of the sample.

FIG. 5 illustrates a process flow diagram 500 depicting a method fordefect detection and photoluminescence measurement of a sample. In step502, a beam of normal-illumination wavelength light is directed onto aportion of the sample along a direction substantially normal to thesurface of the sample. In one embodiment, the beam of light of thenormal-illumination wavelength is suitable for causing one or morephotoluminescing defects of the sample to emit photoluminescent light.In step 504, radiation from the sample is collected. In one embodiment,the radiation from the sample including at least one of radiationelastically scattered by one or more defects of the sample orphotoluminescence radiation emitted by the one or more photoluminescingdefects of the sample. In step 506, the radiation from the sample isseparated into a plurality of portions of photoluminescent radiation,each portion including one or more wavelengths in a different spectralrange of the light emitted by the one or more photoluminescing defectsof the sample. In step 508, one or more characteristics of each of theplurality of portions of photoluminescent radiation are measured. Instep 510, one or more photoluminescence defects are detected based onthe measured one or more characteristics of each of the plurality ofportions of photoluminescent radiation. In step 512, the one or moredetected photoluminescence defects are classified based on one or moresignals associated with each of the plurality of portions ofphotoluminescent radiation.

FIG. 6 illustrates a process flow diagram 600 depicting a method fordefect detection and photoluminescence measurement of a sample. In step602, a beam of normal-illumination wavelength light is directed onto aportion of the sample along a direction substantially normal to thesurface of the sample. In one embodiment, the beam of light of thenormal-illumination wavelength is suitable for causing one or morephotoluminescing defects of the sample to emit photoluminescent light.In step 604, a beam of oblique-illumination wavelength light is directedonto a portion of the sample along a direction along a direction obliqueto the surface of the sample. In step 606, radiation from the sample iscollected. In one embodiment, the radiation from the sample includes atleast one of radiation elastically scattered by one or more defects ofthe sample or photoluminescence radiation emitted by the one or morephotoluminescing defects of the sample. In step 608, the radiation fromthe sample is separated into a visible portion of photoluminescentradiation and a near ultraviolet (NUV) portion of photoluminescentradiation. In step 610, one or more characteristics of the visibleportion of photoluminescent radiation and the NUV portion ofphotoluminescent radiation are measured. In step 612, one or morephotoluminescence defects are detected based on the measured one or morecharacteristics of the visible portion of photoluminescent radiation andthe NUV portion of photoluminescent radiation. In step 614, the one ormore detected photoluminescence defects are classified based on one ormore signals associated with the visible portion of photoluminescentradiation and the NUV portion of photoluminescent radiation.

Those skilled in the art will recognize that it is common within the artto describe devices and/or processes in the fashion set forth herein,and thereafter use engineering practices to integrate such describeddevices and/or processes into data processing systems. That is, at leasta portion of the devices and/or processes described herein can beintegrated into a data processing system via a reasonable amount ofexperimentation. Those having skill in the art will recognize that atypical data processing system generally includes one or more of asystem unit housing, a video display device, a memory such as volatileand non-volatile memory, processors such as microprocessors and digitalsignal processors, computational entities such as operating systems,drivers, graphical user interfaces, and applications programs, one ormore interaction devices, such as a touch pad or screen, and/or controlsystems including feedback loops and control motors (e.g., feedback forsensing position and/or velocity; control motors for moving and/oradjusting components and/or quantities). A typical data processingsystem may be implemented utilizing any suitable commercially availablecomponents, such as those typically found in datacomputing/communication and/or network computing/communication systems.

While particular aspects of the present subject matter described hereinhave been shown and described, it will be apparent to those skilled inthe art that, based upon the teachings herein, changes and modificationsmay be made without departing from the subject matter described hereinand its broader aspects and, therefore, the appended claims are toencompass within their scope all such changes and modifications as arewithin the true spirit and scope of the subject matter described herein.

Although particular embodiments of this invention have been illustrated,it is apparent that various modifications and embodiments of theinvention may be made by those skilled in the art without departing fromthe scope and spirit of the foregoing disclosure. Accordingly, the scopeof the invention should be limited only by the claims appended hereto.It is believed that the present disclosure and many of its attendantadvantages will be understood by the foregoing description, and it willbe apparent that various changes may be made in the form, constructionand arrangement of the components without departing from the disclosedsubject matter or without sacrificing all of its material advantages.The form described is merely explanatory, and it is the intention of thefollowing claims to encompass and include such changes.

What is claimed is:
 1. A system for defect detection andphotoluminescence measurement of a sample comprising: a first radiationsource configured to direct a first beam of light onto a portion of thesample; a second radiation source configured to direct a second beam oflight onto a portion of the sample, wherein the second beam of light issuitable for causing one or more photoluminescing defects of the sampleto emit photoluminescent light; a set of collection optics configured tocollect radiation from the sample, the radiation from the sampleincluding at least photoluminescence radiation emitted by the one ormore photoluminescing defects of the sample; a filter sub-systemconfigured to receive at least a portion of the radiation collected bythe set of collection optics, wherein the filter sub-system isconfigured to separate the radiation from the sample into two or moreportions of radiation, wherein at least a first portion of radiationincludes one or more wavelengths in the visible or near-infraredspectrum associated with the light emitted by the one or morephotoluminescing defects of the sample; a detection sub-system includingat least a first sensor for measuring one or more characteristics of thefirst portion of radiation transmitted by the filter sub-system; and acontroller communicatively coupled to at least the first sensor, thecontroller configured to detect one or more photoluminescence defectsbased on at least the one or more characteristics measured by the firstsensor.
 2. The system of claim 1, wherein the controller is furtherconfigured to detect one or more photoluminescence defects based on atleast the one or more characteristics measured by the first sensor bycomparing a signal from the first sensor in an area of the sample absentof photoluminescing defects to a signal from the first sensor acquiredfrom a measured region of the sample.
 3. The system of claim 1, whereinthe controller is further configured to map the detected one or morephotoluminescence defects based on at least the one or morecharacteristics measured by the first sensor and a position of thedetected one or more photoluminescence defects.
 4. The system of claim1, wherein the controller is further configured to classify the detectedone or more photoluminescence defects based on at least the one or morecharacteristics measured by the first sensor.
 5. The system of claim 1,wherein the one or more photoluminescing defects of the sample comprise:at least one of one or more stacking fault defects and one or more basalplane dislocations.
 6. The system of claim 1, wherein the sample is asemiconductor device.
 7. The system of claim 6, wherein thesemiconductor device is a wide-bandgap semiconductor device.
 8. Thesystem of claim 1, wherein at least one of the first radiation sourceand the second source is a laser.
 9. The system of claim 8, wherein atleast one of the first radiation source and the second source is anultraviolet laser.
 10. The system of claim 8, wherein at least one ofthe first radiation source and the second source is a continuous wave(CW) laser.
 11. The system of claim 1, further comprising: a samplestage assembly configured to secure the sample and selectively actuatethe sample in order to perform a scanning process with at least thefirst radiation source and the second source.
 12. The system of claim 1,wherein the first sensor includes a photomultiplier tube (PMT).
 13. Thesystem of claim 1, wherein the first sensor is configured to measure atleast one of visible photoluminescence light and near-infrared lightemitted from one or more photoluminescent defects of the sample.
 14. Thesystem of claim 1, further comprising: a second sensor configured tomeasure scattered radiation from one or more defects of the sample at awavelength corresponding with the light emitted by the second radiationsource.
 15. The system of claim 14, further comprising: a third sensorconfigured to measure scattered radiation from one or more defects ofthe sample at a wavelength corresponding with the light emitted by thefirst radiation source.
 16. The system of claim 15, wherein at least oneof the second sensor and third sensor is configured to measureultraviolet photoluminescence light from one or more photoluminescentdefects of the sample.
 17. A system for defect detection andphotoluminescence measurement of a sample comprising: a first radiationsource configured to direct a first beam of light onto a portion of thesample; a second radiation source configured to direct a second beam oflight onto a portion of the sample, wherein the second beam of light issuitable for causing one or more photoluminescing defects of the sampleto emit photoluminescent light; a set of collection optics configured tocollect radiation from the sample, the radiation from the sampleincluding at least photoluminescence radiation emitted by the one ormore photoluminescing defects of the sample; a filter sub-systemconfigured to receive at least a portion of the radiation collected bythe set of collection optics, wherein the filter sub-system isconfigured to separate the radiation from the sample into at least oneof a first portion of radiation including one or more wavelengths in thevisible or near-infrared spectrum associated with the light emitted bythe one or more photoluminescing defects of the sample, a second portionof radiation including light from the first radiation source, a thirdportion of radiation including light from the second radiation source,or at least a fourth portion of radiation including one or morewavelengths in the ultraviolet spectrum associated with thephotoluminescent light emitted by the one or more photoluminescingdefects of the sample; a detection sub-system including at least one ofa first sensor for measuring one or more characteristics of the firstportion of radiation transmitted by the filter sub-system, a secondsensor for measuring one or more characteristics of the second portionof radiation transmitted by the filter sub-system, a third sensor formeasuring one or more characteristics of the third portion of radiationtransmitted by the filter sub-system, or a fourth sensor for measuringone or more characteristics of the fourth portion of radiationtransmitted by the filter sub-system; and a controller communicativelycoupled to at least one of the first sensor, the second sensor or thethird sensor, the controller configured to detect one or morephotoluminescence defects based on the light detected by at least one ofthe first sensor, the second sensor, the third sensor, or the fourthsensor.
 18. The system of claim 17, wherein the one or morephotoluminescing defects of the sample comprise: at least one of one ormore stacking fault defects and one or more basal plane dislocations.19. The system of claim 17, wherein the filter sub-system includes: afirst optical element configured to separate a first spectral range ofradiation including the first portion of radiation from the radiationreceived from the sample and direct the first spectral range ofradiation toward the first sensor; a second optical element configuredto receive radiation from the first optical element not included in thefirst spectral range of radiation, wherein the second optical element isconfigured to separate a second spectral range of radiation includingthe second portion of radiation from the radiation received from thefirst optical element and direct the second spectral range of radiationtoward the second sensor; and a third optical element configured toreceive radiation from the second optical element not included in thefirst spectral range of radiation or the second spectral range ofradiation, wherein the third optical element is configured to at leastseparate a portion of a third spectral range of radiation including thethird portion of radiation from the radiation received from the secondoptical element and direct the third spectral range of radiation towardthe third sensor, the third optical element further configured totransmit radiation not included in the first spectral range ofradiation, the second spectral range of radiation or the third spectralrange of radiation toward the fourth sensor in a fourth spectral rangeof radiation including the fourth portion of radiation.
 20. The systemof claim 19, wherein at least one of the first optical element, thesecond optical element, and the third optical element is a dichroic beamsplitter.
 21. The system of claim 19, further comprising: a first narrowpass filter positioned between the first sensor and the first opticalelement and configured to receive at least a portion of the firstspectral range of radiation and transmit the first portion of radiationto the first sensor and block radiation not included in the firstportion of radiation; a second narrow pass filter positioned between thesecond sensor and the second optical element configured to receive atleast a portion of the second spectral range of radiation and transmitthe second portion of radiation to the second sensor and block radiationnot included in the second portion of radiation; a third narrow passfilter positioned between the third sensor and the third optical elementconfigured to receive at least a portion of the third spectral range ofradiation and transmit the third portion of radiation to the thirdsensor and block radiation not included in the third portion ofradiation; and a fourth narrow pass filter positioned between the fourthsensor and the third optical element configured to receive at least aportion of the fourth spectral range of radiation and transmit thefourth portion of radiation to the fourth sensor and block radiation notincluded in the fourth portion of radiation.
 22. The system of claim 17,wherein at least one of the first sensor, the second sensor, the thirdsensor, and the fourth sensor includes a photomultiplier tube (PMT). 23.The system of claim 17, wherein the controller is further configured toclassify the detected one or more photoluminescence defects based on oneor more spectral characteristics of light detected by at least one ofthe first sensor, the second sensor, the third sensor, and the fourthsensor.
 24. The system of claim 17, wherein the sample is asemiconductor device.
 25. The system of claim 24, wherein thesemiconductor device is a wide-bandgap semiconductor device.
 26. Thesystem of claim 17, wherein at least one of the first radiation sourceand the second radiation source is a laser.
 27. The system of claim 26,wherein at least one of the first radiation source and the second sourceis an ultraviolet laser.
 28. The system of claim 26, wherein at leastone of the first radiation source and the second radiation source is acontinuous wave (CW) laser.
 29. The system of claim 17, wherein thefirst sensor is configured to measure at least one of visiblephotoluminescence light and near-infrared light emitted from one or morephotoluminescent defects of the sample and the fourth sensor isconfigured to measure ultraviolet photoluminescence light.
 30. Thesystem of claim 17, wherein the second sensor is configured to measurescattered radiation from one or more defects of the sample at awavelength corresponding with the light emitted by the second radiationsource.
 31. The system of claim 17, wherein the third sensor isconfigured to measure scattered radiation from one or more defects ofthe sample at a wavelength corresponding with the light emitted by thefirst radiation source.
 32. The system of claim 17, wherein at least oneof the second sensor and third sensor is configured to measureultraviolet photoluminescence light from one or more photoluminescentdefects of the sample.
 33. A system for defect detection andphotoluminescence measurement of a sample comprising: a radiation sourceconfigured to direct a beam of light of a first wavelength onto aportion of the sample, wherein the beam of light of the first wavelengthis suitable for causing one or more photoluminescing defects of thesample to emit photoluminescent light; a set of collection opticsconfigured to collect radiation from the sample, the radiation from thesample including at least photoluminescence radiation emitted by the oneor more photoluminescing defects of the sample; a filter sub-systemconfigured to receive at least a portion of the radiation collected bythe set of collection optics, wherein the filter sub-system isconfigured to separate the radiation from the sample into two or moreportions of radiation, wherein at least a first portion of radiationincludes one or more wavelengths in the visible or near-infraredspectrum associated with the light emitted by the one or morephotoluminescing defects of the sample, and at least a second portion ofradiation including one or more wavelengths in the ultraviolet spectrumassociated with the light emitted by the one or more photoluminescingdefects of the sample; a detection sub-system including at least one ofa first sensor for measuring one or more characteristics of the firstportion of radiation transmitted by the filter sub-system or a secondsensor for measuring one or more characteristics of the second portionof radiation transmitted by the filter sub-system; and a controllercommunicatively coupled to the first sensor and the second sensor, thecontroller configured to detect one or more photoluminescence defectsbased on the light detected by at least one of the first sensor or thesecond sensor.
 34. The system of claim 33, wherein at least one of thefirst sensor and the second sensor are configured to measure ultravioletphotoluminescence light or near-ultraviolet photoluminescence light fromone or more photoluminescent defects of the sample.
 35. A system fordefect detection and photoluminescence measurement of a samplecomprising: a first radiation source configured to direct a beam oflight of a first wavelength onto a portion of the sample, wherein thebeam of light of the first wavelength is suitable for causing one ormore photoluminescing defects of the sample to emit photoluminescentlight; a set of collection optics configured to collect radiation fromthe sample, the radiation from the sample including at leastphotoluminescence radiation emitted by the one or more photoluminescingdefects of the sample; a filter sub-system configured to receive atleast a portion of the radiation collected by the set of collectionoptics, wherein the filter sub-system is configured to separate theradiation from the sample into a plurality of portions ofphotoluminescent radiation, each portion including one or morewavelengths in a different spectral range of the radiation emitted bythe one or more photoluminescing defects of the sample; a detectionsub-system including a plurality of sensors, each sensor suitable formeasuring one or more characteristics of one of the plurality ofportions of photoluminescent radiation transmitted by the filtersub-system; and a controller communicatively coupled to each of theplurality of sensors, the controller configured to detect one or morephotoluminescence defects based on the light detected by each of theplurality of sensors.
 36. The system of claim 35, wherein the controlleris further configured to: classify the one or more detectedphotoluminescence defects based on one or more signals measured by eachof the plurality of sensors.
 37. The system of claim 35, furthercomprising: a second radiation source configured to direct a beam oflight of a second wavelength onto a portion of the sample.
 38. Thesystem of claim 37, wherein the filter sub-system is further configuredto separate the radiation into at least one of a portion of radiationincluding the first wavelength and at least an additional portion ofradiation including the second wavelength.
 39. The system of claim 38,wherein the detection sub-system includes at least one of a sensorsuitable for measuring one or more characteristics of the portion ofradiation including the first wavelength transmitted by the filtersub-system and an additional sensor suitable for measuring the at leastan additional portion of radiation including the second wavelengthtransmitted by the filter sub-system.
 40. The system of claim 39,wherein the controller is further configured to detect one or morescattering defects based on the light measured by at least one of thesensor suitable for measuring one or more characteristics of the portionof radiation including the first wavelength and the additional sensorsuitable for measuring the at least an additional portion of radiationincluding the second wavelength.
 41. The system of claim 35, wherein thefilter sub-system includes a plurality of optical elements and aplurality of narrow band filters in order to separate the radiationreceived from the sample into a plurality of spectral bins.
 42. Thesystem of claim 41, wherein the plurality of optical elements and theplurality of narrow band filters define each of the plurality ofspectral bins according to one or more anticipated spectralcharacteristics of one or more photoluminescent defects of the sample.43. The system of claim 42, wherein the plurality of optical elementsand the plurality of narrow band filters substantially match a pluralityof full width half maximum values to a set of corresponding intensitypeaks of a photoluminescent spectrum, wherein each intensity peak isindicative of the presence of a type of stacking fault.
 44. The systemof claim 35, wherein the filter sub-system includes a plurality ofoptical elements and a plurality of narrow band filters in order toseparate the radiation received from the sample into at least one of aplurality of NUV spectral bins, a plurality of UV bins, and a pluralityof visible spectral bins.
 45. A method for defect detection andphotoluminescence measurement of a sample comprising: directing a beamof first wavelength light onto a portion of the sample; directing a beamof second wavelength light onto a portion of the sample, wherein thebeam of light of the second wavelength is suitable for causing one ormore photoluminescing defects of the sample to emit photoluminescentlight; collecting radiation from the sample, the radiation from thesample including at least photoluminescence radiation emitted by the oneor more photoluminescing defects of the sample; separating the radiationfrom the sample into two or more portions of radiation, wherein at leasta first portion of radiation includes one or more wavelengths in thevisible or near-infrared spectrum associated with the light emitted bythe one or more photoluminescing defects of the sample; measuring one ormore characteristics of the first portion of radiation; and detectingone or more photoluminescence defects based on the measured one or morecharacteristics of at least one of the first portion of radiation.
 46. Amethod for defect detection and photoluminescence measurement of asample comprising: directing a beam of first wavelength light onto aportion of the sample; directing a beam of second wavelength light ontoa portion of the sample, wherein the beam of light of the secondwavelength is suitable for causing one or more photoluminescing defectsof the sample to emit photoluminescent light; collecting radiation fromthe sample, the radiation from the sample including at leastphotoluminescence radiation emitted by the one or more photoluminescingdefects of the sample; separating the radiation from the sample into atleast one of a first portion of radiation including one or morewavelengths in the visible or near-infrared spectrum associated with thelight emitted by the one or more photoluminescing defects of the sample,a second portion of radiation including light from the first radiationsource, a third portion of radiation including light from the secondradiation source, or at least a fourth portion of radiation includingone or more wavelengths in the ultraviolet spectrum associated with thephotoluminescent light emitted by the one or more photoluminescingdefects of the sample; measuring one or more characteristics of at leastone of the first portion of radiation, one or more characteristics ofthe second portion of radiation, one or more characteristics of thethird portion of radiation, or one or more characteristics of the fourthportion of radiation; detecting one or more scattering defects based onthe measured one or more characteristics of at least one of the secondportion of radiation and the third portion of radiation; and detectingone or more photoluminescence defects based on the measured one or morecharacteristics of at least one of the first portion of radiation, thesecond portion of radiation, the third portion of radiation, or thefourth portion of radiation.
 47. A method for defect detection andphotoluminescence measurement of a sample comprising: directing a beamof first wavelength light onto a surface of the sample, wherein the beamof light of the first wavelength is suitable for causing one or morephotoluminescing defects of the sample to emit photoluminescent light;collecting radiation from the sample, the radiation from the sampleincluding at least photoluminescence radiation emitted by the one ormore photoluminescing defects of the sample; separating the radiationfrom the sample into two or more portions of radiation, wherein at leasta first portion of radiation includes one or more wavelengths in thevisible or near-infrared spectrum associated with the light emitted bythe one or more photoluminescing defects of the sample, and at least asecond portion of radiation including one or more wavelengths in theultraviolet spectrum associated with the light emitted by the one ormore photoluminescing defects of the sample; measuring one or morecharacteristics of at least one of the first portion of radiation or oneor more characteristics of the second portion of radiation; anddetecting one or more photoluminescence defects based on the lightdetected by at least one of the first sensor or the second sensor.
 48. Amethod for defect detection and photoluminescence measurement of asample comprising: directing a beam of light of a first wavelength ontoa portion of the sample, wherein the beam of light of the firstwavelength is suitable for causing one or more photoluminescing defectsof the sample to emit photoluminescent light; collecting radiation fromthe sample, the radiation from the sample including at leastphotoluminescence radiation emitted by the one or more photoluminescingdefects of the sample; separating the radiation from the sample into aplurality of portions of photoluminescent radiation, each portionincluding one or more wavelengths in a different spectral range of thelight emitted by the one or more photoluminescing defects of the sample;measuring one or more characteristics of each of the plurality ofportions of photoluminescent radiation; and detecting one or morephotoluminescence defects based on the measured one or morecharacteristics of each of the plurality of portions of photoluminescentradiation.
 49. A method for defect detection and photoluminescencemeasurement of a sample comprising: directing a beam of first wavelengthlight onto a portion of the sample, wherein the beam of light of thefirst wavelength is suitable for causing one or more photoluminescingdefects of the sample to emit photoluminescent light; directing a beamof second wavelength light onto a portion of the sample; collectingradiation from the sample, the radiation from the sample including atleast photoluminescence radiation emitted by the one or morephotoluminescing defects of the sample; separating the radiation fromthe sample into a visible portion of photoluminescent radiation and anear-ultraviolet (NUV) portion of photoluminescent radiation; measuringone or more characteristics of the visible portion of photoluminescentradiation and the NUV portion of photoluminescent radiation; anddetecting one or more photoluminescence defects based on the measuredone or more characteristics of the visible portion of photoluminescentradiation and the NUV portion of photoluminescent radiation.
 50. Thesystem of claim 49, further comprising: classifying the one or moredetected photoluminescence defects based on one or more signalsassociated with the visible portion of photoluminescent radiation andthe NUV portion of photoluminescent radiation.